[Samba] Failover DC did not work when Main DC failed

Kris Lou klou at themusiclink.net
Wed Jan 29 18:03:37 UTC 2020

My understanding is that Windows clients periodically hold elections to
verify and select their closest DC.  However, I'm not 100% sure how often
it holds these elections, or what the DC response timeout is before holding
new elections.

A nice summary is here:

However, I'm not sure about winbind.  In my case, I've observed a member
server (older QNAP running Debian+Louis) ignore sites and reach across a
VPN to a remote DC.  It might be purely DNS?

Kris Lou
klou at themusiclink.net

On Wed, Jan 29, 2020 at 8:43 AM Rowland penny via samba <
samba at lists.samba.org> wrote:

> On 29/01/2020 15:55, Paul Littlefield via samba wrote:
> > We have a main DC (dc3) and failover DC (dc4) running in a Proxmox
> > virtual environment.
> >
> > Both DCs are replicating happily and have been running for over a year
> > with no problems.
> >
> > This morning, our main DC (running as a VM) was backed up and then
> > restarted but Ubuntu did not start the 'samba-ad-dc' service on boot.
> >
> > The failover DC was up and running at the time, but staff could not
> > log in on their workstations and the QNAP file server (which is domain
> > joined) was also not happy.
> >
> > The fix was to reboot and everything was well again.
> >
> > Lesson learned... check port 135 as well as port 22 on Nagios, and
> > check that the failover DC works!
> >
> > My question... why didn't the failover DC do its job?
> >
> > Thanks,
> >
> > Paul
> >
> >
> OK, where did you get the 'failover' DC from ?
> As far as I am aware, all DC's are equal except for the FSMO roles and
> these can be on any DC. So terms like 'pdc', 'backup' and 'failover' are
> meaningless, they are all just a 'DC'.
> It sounds like your clients are set up to just use the DC that went down
> as their nameserver etc.
> Rowland
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